The patch below does not apply to the 5.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From dd75080aa8409ce10d50fb58981c6b59bf8707d3 Mon Sep 17 00:00:00 2001 From: Chen Jingwen chenjingwen6@huawei.com Date: Wed, 29 Dec 2021 11:52:26 +0800 Subject: [PATCH] powerpc/kasan: Fix early region not updated correctly

The shadow's page table is not updated when PTE_RPN_SHIFT is 24 and PAGE_SHIFT is 12. It not only causes false positives but also false negative as shown the following text.

Fix it by bringing the logic of kasan_early_shadow_page_entry here.

1. False Positive: ================================================================== BUG: KASAN: vmalloc-out-of-bounds in pcpu_alloc+0x508/0xa50 Write of size 16 at addr f57f3be0 by task swapper/0/1

CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.15.0-12267-gdebe436e77c7 #1 Call Trace: [c80d1c20] [c07fe7b8] dump_stack_lvl+0x4c/0x6c (unreliable) [c80d1c40] [c02ff668] print_address_description.constprop.0+0x88/0x300 [c80d1c70] [c02ff45c] kasan_report+0x1ec/0x200 [c80d1cb0] [c0300b20] kasan_check_range+0x160/0x2f0 [c80d1cc0] [c03018a4] memset+0x34/0x90 [c80d1ce0] [c0280108] pcpu_alloc+0x508/0xa50 [c80d1d40] [c02fd7bc] __kmem_cache_create+0xfc/0x570 [c80d1d70] [c0283d64] kmem_cache_create_usercopy+0x274/0x3e0 [c80d1db0] [c2036580] init_sd+0xc4/0x1d0 [c80d1de0] [c00044a0] do_one_initcall+0xc0/0x33c [c80d1eb0] [c2001624] kernel_init_freeable+0x2c8/0x384 [c80d1ef0] [c0004b14] kernel_init+0x24/0x170 [c80d1f10] [c001b26c] ret_from_kernel_thread+0x5c/0x64

Memory state around the buggy address: f57f3a80: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f57f3b00: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8

f57f3b80: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8

^ f57f3c00: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f57f3c80: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 ==================================================================

2. False Negative (with KASAN tests): ================================================================== Before fix: ok 45 - kmalloc_double_kzfree # vmalloc_oob: EXPECTATION FAILED at lib/test_kasan.c:1039 KASAN failure expected in "((volatile char *)area)[3100]", but none occurred not ok 46 - vmalloc_oob not ok 1 - kasan

================================================================== After fix: ok 1 - kasan

Fixes: cbd18991e24fe ("powerpc/mm: Fix an Oops in kasan_mmu_init()") Cc: stable@vger.kernel.org # 5.4.x Signed-off-by: Chen Jingwen chenjingwen6@huawei.com Reviewed-by: Christophe Leroy christophe.leroy@csgroup.eu Signed-off-by: Michael Ellerman mpe@ellerman.id.au Link: https://lore.kernel.org/r/20211229035226.59159-1-chenjingwen6@huawei.com

diff --git a/arch/powerpc/mm/kasan/kasan_init_32.c b/arch/powerpc/mm/kasan/kasan_init_32.c index cf8770b1a692..f3e4d069e0ba 100644 --- a/arch/powerpc/mm/kasan/kasan_init_32.c +++ b/arch/powerpc/mm/kasan/kasan_init_32.c @@ -83,13 +83,12 @@ void __init kasan_update_early_region(unsigned long k_start, unsigned long k_end, pte_t pte) { unsigned long k_cur; - phys_addr_t pa = __pa(kasan_early_shadow_page);

for (k_cur = k_start; k_cur != k_end; k_cur += PAGE_SIZE) { pmd_t *pmd = pmd_off_k(k_cur); pte_t *ptep = pte_offset_kernel(pmd, k_cur);

- if ((pte_val(*ptep) & PTE_RPN_MASK) != pa) + if (pte_page(*ptep) != virt_to_page(lm_alias(kasan_early_shadow_page))) continue;

__set_pte_at(&init_mm, k_cur, ptep, pte, 0);